Purification of ketone-containing liquid



` Oct. 2, 1951 E. A. RODMAN PURIFICATICN oF KEToNE-CONTAINING LIQUD Filed June'4, 194e l .mmmzmoZOnY Nwmoo Nouv-muslo )INVL SNIBDSVSW HEISNBGNOO N 'fla-uno Y IN VEN TOR. Y

rnest A Rodzzz al@ M Q' ij? ATTORNEY Patented Oct. 2`, 1951 LgygUNlTED STATES PATENT OFFICE;

l PURIFICA'rIoNoF KE'roNE-coNTAINiNG LIQUID Ernest A. Rodman, Newburgh, N. Y., assignor t0 E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application June 4, 1946, Serial No. 674,343 4 claims. (C1.` 26o-593)` j This invention relates to a process for the puri- Vfication of organic liquids and particularly to theV removal of diketones from organic liquids.

In the manufacture of coating compositions, `ketones are widely employed as a solvent or a portion of the organic solvent for the lm forming components of the coating compositions. In certain industrial processes such as the coating of fabrics, automobile bodies, etc., with lm forming compositions it is common practice to recover the organic solvents after the composition has been applied to whatever surface is being coated. The solvent recovery is generally accomplished by drawing air and the organicsolvent vapors ,into an enclosed tank containing a bed of activated carbon. The organic solvent or solvent Vmixture is adsorbed by the activated carbon. As soon as the carbon bed becomessaturated, .the solvent is steam distilled from the carbon beds and the distillate of water and organic solvents is then rectified or separated into the individual components by distillation.

In the recovery of organic solvents containing ketones having 4 or more carbon atoms, even in small proportions, the activated carbon acts as a catalyst in the oxidation of the ketone to diketones as indicated by the following typical reac- ,toin in which methyl ethyl ketone is oxidized to diacetyl: i

o nac-'t'J-cnz-cn o2 H3cy3cn3 H20 The reaction between the ketone and oxygen willalso'take place in the absence of a catalyst such as activated carbon when the ketone is brought in contact with oxygen at'elevated temperatures. The diketones in contradistinction to the -colorless aliphatic monoketones are yellow volatile liquids with a penetrating quinone-like odor.V The presence of diketones in organic solvent is objectionable for several reasons, such aS, objectionable color, its chemical reactivity, and its undesirable physiological effect on some `individuals coming in contact with the diketones.

It is generally impossible to remove diketones from the monoketones, from which they are lformed by oxidation, by the process of distillaftion due to the formation of azeotropes. The primary object of this invention is the provision of a method for the removal of diketones from organic solvents and more particularly the removal of diacetyl from organic solvents. A still more particular object is the removal of diacetyl from methyl ethyl ketone. These objects are accomplished by the reduc- `tionof the diketone in the presence of an organic `solvent or mixture of organic solvents by treatment with nascent hydrogen, and separating by -distillation the organic solvents from the reduction products.

,ethyl ketone.

In the drawing the single gure is a ow sheet for the treatment of organic liquids in accordance with this invention. Throughout the description of the invention the numerical refermethyl ethyl ketone is used as the solvent for forming a solution of the vinyl resin. Thevinyl resin coating composition usually comprises polyvinylchlorida. pigments, plasticizers, and methyl The coated fabric is passed through a heated chamber immediately after each successive coat to evaporate the methyl ethyl ketone. The mixture of methyl ethyl ketone vapor and air including some water vapor is drawn into a closed tank l with a bed of activated carbon 2. The methyl ethyl ketone is adsorbed by the activated carbon. When theactivated carbon bed becomes saturated, it is then closed off from the source of solvent vapor by .means of valves 3 and 4, and air and steam are 'todiacetyL particularly at elevated temperatures. .Also formed along with the diacetyl are some 4acidic products, particularly acetic acid, by the decomposition of methyl ethyl ketone. The diacetyl is a yellow colored material which forms van azeotrope with methyl ethyl ketone and cannot be separated by conventional distillation methods.. Besides imparting a yellow color to the recovered solvent the diacetyl will produce `undesirable physiological effects on individuals coming in contact with it. As little as 0.01% of `dicetyl in methyl ethyl ketone is suilicient to result in the undesirable yellow color to thelatter. The distillate, containing methyl ethyl ketone,

"diacetyl, acid decomposition products, and water, is collected from the `condenser 6 and passed through a measuring tank 'l and is then circulated through a bed of mossy zinc metalB in one end of tank 2l by means of pump 9. The uid mixture is circulated through the Zinc bed 8 by means of a pump 9 and openingvalves 22 and 23 and closing valves 24 and 25, and passed through a :heater IIJ to raise the temperature of the uid mixture up to about 125 C. The heatedfluid mixture is circulated through the zinc bed 8 until the diacetyl content is reduced to about .001%.

The acid components of the liquid being treated react with the zinc to form nascent hydrogen which reduces the diacetyl to less volatile products from which the methyl ethyl ketone can be 3 separated by distillation. It is believed that the reduction takesplace in a manner as outlined below:

The reaction between the acid'pro'ducts and zinc to liberate nascent hydrogen, which reduces the diacetyl to butylene glycol and acetoin as indicated above, is accelerated at elevated temperatures. For the purposeA of this invention the optimum temperature appears to be 45 C. (113 FD". In any eventI the temperaturel of the liquid being circulated through the zinc'bed should not exceed the boilingrpoint of the liquid'.

"The methyl ethyl ketone and water form an aneotrope` (88.7% methyl ethyl ketone-11.3% water) vwhich boils at 73.4 C. andV is' separated from the reduction products by distilling in col'- vumn l2, heated by sparger 25', after passing through the constant level'tank' II. The residue consists of the reduction products and water. The reduction products being Water soluble are washed free from the still when theresidue is drained through' valve I 3. ing of the azeotrope of methyl ethyl ketone and water isy waterwhite and free from the" objectionable decomposition products of methyl ethyl ketonea y 'il-hel distillate from column I2 passes Vthrough the dephlegmator I4 and condenser I5 and' the azeotrope is collected in tank I5. The ajzeotrope ofv methyl ethyl ketone andy waterv is treatedin tank I- with calcium chloride or other dehydrating agents to remove substantially all thewat'er. .The water content of the azeotrope is reduced tofl below 1% by this treatment. To dehydrate the methyl ethyl ketone further, it is again distilled in pot still I8, heatedbyA means of steam coils 21, and the Vremaining 1% or less ofwater comes over as an azeotrope with methyl ethyl ketone as the rst fraction which` is returned for dehydration and again treated. The substantially pure methyl ethyl ketone passes 'through condenser I9- and` isV collected in storage tank 20; Y Y

While the above description alludes tothe purification of methyl ethyl ketone,l the invention can also Ybey used in purifying other solvents which contain diketones, such as alcohols, esters,

'hydrocarbons and ketones or mixtures thereof.l

a solvent recoverysystem where'the carbon beds ,areA used alternately with methyl ethyl ketone-and aV mixture off ethyl alcohol and ethyl acetate, the alcohol-ester mixture will become Iadirli'xed with methyl ethylA ketone. The methyl cth-ylketone present in the solvent mixtures Will oxidize toV diacetyl and impart a yellow color to the reclaimed solvents. The diacetyl can, be removed from the solvent mixtures by the same reduction process as outlined above for the purification; of methyl ethyl ketone.

In' the case ofthe purification of mixtures of ethyl alcohol and ethyl acetate containing dfiacetyl' resulting from the oxidation of methyl ethyl ketone, the process comprises circulating v the liquid to be purified which is slightlyV acid in-a'tank containing-mosey Zinc metal. The acid present in the liquid being puriiied results from l vthe hydrolysis of a small amount of ethyl acetate,

:the oxidation cfa small amount of the alcohol The distillate consistto acetaldehydeand acetic acid, and oxidation of a portion of the diacetyl. The acidic material reacts with the zinc liberating nascent hydrogen which reduces the diacetyl as outlined above. The products of the reduction of diacetyl as well as the hydrolysis of diacetyl are separated from the ethyl alcohol, ethyl acetate and other solvents by rectification or distillation as outlined above for the purification of methyl ethyl ketone.

While the preferred embodiment of the invention is the purication of organic solvents containing diacetyl, the invention is also useful for the separation from organic liquids of other diketones and ketoaldehydes formed by the oxidation of monoketones other than methylethyl ketone. The diketones and ketoaldehydes formed bythe oxidation oi'V monoketones which may be separated ,from other organic liquids by this invention asv outlined above are those formed by the oxidation of monoketones as represented by the following formula:

o o` o mno-h-cnm IV o2v Q smc-h-hn -I- H20 Where R is hydrogen oran alkyl radical having one orvmore carbon atoms.

" It wilr bey readily apparent that manyrwidely diierent embodiments of this invention may be made without departing from the spirit and'scope thereof; and, therefore, it is not intended to be limited except as indicated in the appended ethyl ketone and avolatile saponiable ester and containing a small amount of free acid and a relatively'smaill amount of diacetyl as an impurity Y 3. The method of. claim 1 in which the organic liquid' contains a small amount of` acetic acid andthe nascent hydrogen is produced by reacting the acetic acid with zinc metal. Y

4. The method of claim l in which the reduction takes place at about 45 C.

' ERNESTv A. RODMAN.

REFERENCES CITED The following references are of record in the Iileof this patent.:

y UNITED STATES PATENTS .Number K Name Date 1,089,775 Lindner Mar. 10, 1914 y.. 1,681,238 James Aug. 21, 1928 1,979,303 Woodhouse Nov. 6, 1934 2,205,184y WOOdhOuSe June 18, 19h40 2,276,142 Atwood Mar. 10, 1943 f 2,429,484 Peters Oct. 2l., 1947 Y REFERENCES Peckmann': Berichte, vol. 21, pages 1411-1422 fuese); v01. 22, pages 2214-15v (1889 v01; 23, pages 2421-2427 (1890).

Englund: J. frV Praktische Chemie, Second "Series, vol. 124, pages 191-208 (only page 193 necessary) (1930) 

1. THE METHOD OF PURIFYING ORGANIC LIQUIDS COMPRISING IN PREDOMINATING AMOUNT METHYL ETHYL KETONE AND A VOLATILE SAPONIFICATIABLE ESTER AND CONTAINING A SMALL AMOUNT OF FREE ACID AND A RELATIVELY SMALL AMOUNT OF DIACETYL BUT WHICH COMPRISES REDUCING THE SAID DIACETYL BUT NOT THE MAIN BODY OF THE ORGANIC LIQUID WITH NASCENT HYDROGEN, PRODUCED BY REACTION OF THE SAID ACID AND A METAL, TO A MIXTURE OF BUYTLENE GLYCOL AND ACETOIN, AND THEREAFTER SEPARATING THE SAID ORGANIC LIQUID FROM THE REDUCTION PRODUCTS BY FRACTIONAL DISTILLATION. 